Sedimentation in a stratified ambient

We study the interaction between settling particles and a stratified ambient in a variety of contexts. We first study the generation of large scale fluid motions by the localised release of a finite mass of particles in the form of plumes or gravity currents. We present the results of a combined theoretical and experimental study describing the evolution of particle clouds formed by the release of heavy particles. In the early stages of motion, particle clouds behave as turbulent fluid thermals; however, their radial expansion eventually stops and particles settle from the base of the cloud at their individual settling speed. We focus on deducing a criterion for the various modes of particle deposition from particle clouds in a stratified ambient. We proceed to study the deposition patterns resulting from particle-laden gravity currents that spread horizontally when released in a particle-free ambient. Using a box-model, we focus on bidisperse gravity currents and examine the resulting particle distribution and maximal deposit length. We then turn to suspensions where particles are initially present throughout the fluid. The simultaneous presence of particles and of a stratified ambient may lead to behaviour analogous to double-diffusive systems, with particles playing the role of a diffusing component. We examine the linear stability of the settling of a particle concentration gradient in a stratified fluid. Numerical simulations allow us to determine the stability of the system for a broad range of particle settling speeds and diffusion coefficients. We then report on layering arising from sedimentation in a density stratified ambient beneath an inclined wall.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mathematics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Blanchette, François Alain, 1978-

Advisor dc:contributor.advisor

• John W.M. Bush.

• Mathematics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/29986

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/29986